1. Technical Field
This application relates to ultrasound imaging systems, for instance medical diagnostic ultrasound imaging systems and, in particular, to the use of information contained in ultrasound return signals to operate the ultrasound imaging system.
2. Description of the Related Art
Ultrasound imaging systems employ transducer arrays to produce and transmit ultrasound pressure waves into an object such as a body, tissue or other material. The transducer arrays also receive ultrasound return or echo signals and produce analog transducer element voltage signals which are induced at the transducer array by the received ultrasound return or echo signals.
Many ultrasound imaging systems are capable of operating in various modes for sampling, processing and/or presenting ultrasound information in a variety of useful representations. For example, ultrasound systems may employ A-, B-, M-, Doppler, energy, power, Doppler amplitude or color angio modes. Some ultrasound systems are capable of concurrently displaying information in more than one type of representation.
A region in three-dimensional space from which data is collected is commonly referred to as a sample volume. The sample volume typically has a width determined by the lateral margins of the ultrasound beam and an axial depth along the ultrasound beam determined by a duration of the transmitted ultrasound pulse and a duration of a sample gate implemented by the circuitry of the ultrasound imaging system.
It is often desirable or even necessary to sample or image a desired location (e.g., three-dimensional location, including axial depth) in a material. For instance, medical imaging typically involves capturing a sample or image of a volume at a desired location in a body or anatomical structure (e.g., bodily organ). In some applications, a sonographer or clinician may locate or place a sample volume with reference to a two-dimensional image (e.g., B-mode image), then switch the ultrasound imaging system into “Doppler” mode to see the “Doppler” waveform.
However, it can be difficult to maintain the sample volume in a desired location. Such may be difficult when there is no or relatively little relative movement between the transducer array and the desired location. Such may be even more difficult when there is relative movement between the transducer array and the desired location, for instance where the transducer array is translated along a tissue or structure such as along an artery. If the ultrasound imaging system has “triple” mode capability or an Echo/Doppler mode, a sonographer or clinician may use a reference to aid in manually maintaining a sample volume in a desired or correct location. However, such may adversely take away acquisition time form Doppler firings, which reduces the ability to view high flow rates.
New approaches that facilitate maintaining a sample volume at desired locations while allowing relatively high pulse repetition frequency (PRF) are desirable.